As long as there have been bridges, trolls have hidden beneath them. Same for the Internet.

As long as there have been message boards, discussion groups and comment strings, there have been “trolls” — people who, under cover of Web anonymity, post bullying, lewd or off-point comments, disrupting and demeaning the whole enterprise.

Some comment strings are moderated, so trolls can be blocked and deleted — but most of cyberspace is, in the words of one anonymous wit, “free range for idiots.”

Just one example, to stand for many, from a Harry Potter site: “ENOUGH already with all this Harry Potter (expletive)! What sort of LOSERS think this stuff is cool??? I swear, the little (indelicate term) should be carved up with rusty scythes and his remains poured into a cement mixer. I am so sick and tired of hearing about Harry (extreme epithet) (other extreme epithet) POTTER!”

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It’s been a problem for years. Julie Spira, an expert on Web etiquette and author of the book “Netiquette,” said, “It started with some of the early Usenet groups, where some of the first ‘flame wars’ broke out among users.”

Some sites — newspapers and entertainment venues — are so encrusted with trolls, like malign barnacles, that comment threads become all but useless. Jolie O’Dell, a reporter for the tech-business blog VentureBeat, said: “I don’t read comments anymore. I’ve learned there’s nothing anyone’s going to say that’s going to meet me at a professional level of discourse.”

People are looking for solutions. Some, like Gayle Lynn Falkenthal, media columnist for Washington Times Communities, have called for an end to anonymity. “And you should have seen the trollery after I did,” she said from San Diego. “It was jaw-dropping.”

She said she values the First Amendment, “but any venue with a public responsibility, such as a newspaper, a media site, anything with public money behind it — no place for anonymity there.”

The past five years have seen the rise of what O’Dell calls “a new breed of employee called the ‘community manager,’ a big part of whose job is policing commentary, allowing for freedom of speech, but deleting profanities, offensive things, trollery.”

More and more venues are hiring community managers because they see their reputations tied to the quality of their online communities.

Where is the comment the smartest and best-behaved? Much-copied moderated websites include the Huffington Post and ABCnews.com. Trollery has inspired much experiment. Chris Satullo, a former Philadelphia Inquirer editor who is executive director of news and public dialogue for Philadelphia radio station WHYY, was a main force behind NewsWorks, the station’s news site.

NewsWorks has an admirably well-thought-out and explicit policy about comments, based on that of NPR.org.

Julia Hobsbawm, who runs the British media, analysis, and networking business Electronic Intelligence, said that mere “peer pressure is often insufficient to self-regulate abusive comment strings,” but she, too, likes media platforms that tie quality to attention.

Web lovers are leery of all this policing and pressuring. But courtesy expert Spira said, “All of us can only gain if, when we comment, we stay on topic, show respect and provide a new perspective on the subject that other users might find interesting.”